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T^NTHRACNOSE DISEASE OF THE 
\SPBERRY AND RELATED PLANTS 



JUN 21 i9lB 



A THESIS 



Presented to the Faculty of the Graduate School 

OF Cornell University for the Degree of 

DOCTOR OF PHILOSOPHY 



BY 



WALTER H. BURKHOLDER 



Reprint of Cornell University Agricultural Experiment Station Bulletin 395, 

November, 191 7 



THE ANTHRACNOSE DISEASE OF THE 
RASPBERRY AND RELATED PLANTS 



A THESIS 

Presented to the Faculty of the Graduate School 

OF Cornell University for the Degree of 

DOCTOR OF PHILOSOPHY 



BY 

WALTER H. BURKHOLDER 



Reprint of Cornell University Agricultural Experiment Station Bulletin 395, 

November, 191 7 



7 



^ 






i.^ ^^ ' 



',f 



CONTENTS 

PAGE 

History and geographical distribution of the disease 159 

Economic importance 159 

Symptoms 160 

On the canes 160 

On petioles and pedicels 163 

On the leaves 163 

Etiology 164 

Mor|3hology 164 

Nomenclature 166 

Life history 167 

The ascigerous stage 167 

The imperfect stage 169 

Pathological histology 170 

Cultural characters 172 

Inoailation experiments 174 

Inoculations with spores from the Gloeosporium stage 174 

Inoculations with spores from the ascigerous stage 175 

Cross-inoculations 177 

The effect of weather conditions 177 

Control 178 

Cultural methods 178 

Spraying 179 

Bibliography 182 



155 



THE ANTHRACNOSE DISEASE OF THE RASPBERRY AND 
RELATED PLANTS^ 

Walter H. Burkholder 

The raspberry is one of the oldest of the small fruits. It belongs to 
the genus Rubus, of the fainih^ Rosaceae,- and comprises a number of 
varieties which with a few exceptions originated from three main sources — 
the European red raspberr\- (Ritbus idaens L.), and the two American 
species, the red raspberry (Riihns idaeus var. acideatissimus [Mey.] Regel 
& Tiling) and the black raspberry (Rubus occidentalis L.). The first 
of these three species was under cultivation as early as the fourth century, 
but the domestication of the other two is of very recent date. 

Most of the commercial varieties of the raspberry in North America 
originated from the two indigenous species, the European red rasp- 
berry not being sufficiently hardy and vigorous to withstand the climatic 
conditions of this countr}\ Two hybrids also are grown extensively 
here. They are the purple-cane raspberry, formerly known as Ruhiis 
neglectus Peck but now claimed by Anthony ^ to be a cross between the 
red and the black raspberr}^ ; and the loganberry, considered to be a hybrid 
between the European red raspberry and the western dewberry (Rubus 
vitijolius Cham. & Schlecht.). 

In the United States these berries are grown throughout the northern 
part of the country and in the cooler hilly regions. According to the 
Thirteenth Census Report, New York State in 1910 ranked first in the 
production of this fmit, with 11,057 acres, and Michigan second, with 
8786 acres; no other State had as much as 4000 acres. In New York 
the raspberry industry is limited to small districts throughout the western 
part of the State, with the exception of an area in the Hudson River 
Valley. In these localities during the past ten years or more there has 
been a marked decrease both in acreage and in yield, which is attributed 
to the general prevalence of diseases to which the host is susceptible. 

The anthracnose disease, yellows, cane blight, and crown gall are the 
commonest diseases affecting the raspberry. Anthracnose occurs in 
practically every locality and is considered the most serious disease of 

' Also presented to the Faculty of the Graduate School of Cornell University, June, 1917, as a thesis in 
partial fulfillment of the requirements for the degree of doctor of philosophy. 

Author's acknowledgments. The writer wishes to express his indebtedness to Professor Donald 
Reddick, under whose direction the work was performed, and to Professor V. B. Stewart for help and 
criticism in preparation of the manuscript. 

- Card, Fred W. The brambles. In Bush-fruits, p. 43-336. 1914. 

' Anthony, R. D. Some notes on the breeding of raspberries. New York (Geneva) Agr. Exp. Sta. 
Bui. 417:75-88. 1916. 



158 Bulletin 395 

the plant. It is known also as cane rust, spot, scab, or sun-scald. It 
occurs on all the above-named species of Rubus and their hybrids, and 
in addition is found on various other species of this genus, such as the 
blackberry {Rubus sp.), the eastern and the western dewberr\^ {Rubus 
villosus Ait. and Rubus vitijolius Cham. & Schlecht.), the cloudberry 
{Rubus chamaemorus L.), and the European bramble {Rubus fruticosus L.). 
Halsted (1894)'' has suggested that the anthracnose of the rose may be 
identical with that of the raspberr^^ but this has not been proved. 

Of the species of Rubus affected by anthracnose, the black raspberry 
{Rubus occidentalis) exhibits the greatest susceptibility to the disease. 
On this species the disease is very severe, not only on the cultivated 
varieties but also on the wild forms. Observations show, moreover, 
that the hybrid generally known as Rubus neglectus has inherited this 
susceptibility, and anthracnose occurs commonly in plantations where 
this hybrid is grown. On the other hand, the commercial varieties of 
the red raspberry, which arise mainly from Rubus idaeus var. aculeaiissimus , 
show a marked resistance to the disease. Very few fields planted with 
these varieties have been obser\^ed where the anthracnose was considered 
to be of any economic importance. Furthermore, it is noticeable that 
on the wild forms of this species the disease seldom occurs except on the 
leaves, where it is never serious. In New York State the blackberry 
is rarely subject to anthracnose, but according to Lawrence (19 10) and 
Jackson (19 13) it is very susceptible to the disease in the northwestern 
United States. Anthracnose is more or less injurious also to the dew- 
berry and the loganberry'. 

Varietal susceptibility is not markedly perceptible within the above- 
named species. Taylor ^ reports a desirable black raspberry, the Hoosier, 
which is considered to be resistant; at least it has remained free from the 
anthracnose disease up to the present time. Among the varieties of the 
red raspberry the Cuthbert is held to be the most resistant, though all 
the varieties of this species exliibit but very little susceptibility. The 
Columbian, a purple-cane variety, formerly was regarded as nearly 
immune, but it now exhibits a marked susceptibility. It is not known 
whether this variety really possessed resistance at one time or whether 
the stock was merely free from the disease. At present very few growers 
recognize an\' difference in susceptibility between the black raspberry 
and the purjile-cane varieties. Lawrence (1910) states that among 
the varieties of blackberry the disease is severe on the Snyder and the 
Kittatany, while on the Himalaya Giant it occurs only on the leaves. 

* Dates in parenthesis refer to bibliography, page 182. 

'- Taylor, William A. Hoosier raspberry. In Promising new fruits. U. S. Dept. Agr. Yearbook 
igiO:42c;-430. 1911. 



The Anthracnose Disease of the Raspberry 159 

HISTORY AND GEOGRAPHICAL DISTRIBUTION OF THE DISEASE 

The anthracnose disease is possibly of as widespread distribution as 
the raspberry itself. Massee (1907) states that it occurs in Europe, 
America, and Australia but has been found more commonly on the last 
two continents. The disease was first reported in Italy, by Spegazzini 
(1879), on the leaves of the cloudberry (Rubus chamaenionis) . The follow- 
ing year it was brought to the attention of Burrill (1882) in America, 
where in certain localities it was causing serious losses to the black rasp- 
bern,^ crop. 

It is thus difficult to determine whether anthracnose is of American 
or European origin. The disease has been more destructive in America, 
doubtless due to the fact that the most susceptible species of the genus 
Rubus are under cultivation here. Cooke (1906) even expresses doubt 
that the disease is to be found in England, and Sorauer (1908) does not 
mention its occurrence in Germany. On the other hand, the disease 
spread rapidly in America, and ten years after it was first noticed, in 
Italy, Scribner (1888) reports it as being widespread and destructive 
in the United States. Deamess collected diseased material in Canada 
in 1 89 1 and contributed it to the exsiccati of Seymour and Earle's 
Economic Fungi. A few years later McAlpine (1897) reported it from 
Australia. 

ECONOMIC IMPORTANCE 

It is difficult to estimate the losses caused by anthracnose, since the 
disease varies greatly with climatic conditions and the host plant is often 
subject to less striking diseases which are nevertheless of considerable 
importance. Such diseases as yellows and crown gall are frequently 
overlooked and their injury to the plant attributed to anthracnose when 
that is present. No doubt the estimates of losses due to anthracnose 
have been in some cases too high, although it is one of the most serious 
diseases of the raspberr}^ For these reasons, and from the fact that the 
disease affects the plant onl}^ indirectly, little data are available showing 
the percentage of loss caused by anthracnose. A few investigators, 
however, have made estimates which may be mentioned here. 

Burrill (1882) cites an instance of a raspberry plantation ordinarilv 
yielding a profit of $400 per year, which profit was reduced to such an 
extent by one attack of anthracnose that expenses were scarcely met. 
Scribner (1888) estimates the losses in southern Missouri on the blackcap 
raspberry as being from ten to twelve per cent of the entire crop. The 
disease is reported by Orton and Ames (1908) to have injured sixty-three 
per cent of the raspberry crop in Nebraska, fifty per cent in Wisconsin, 
and even a greater percentage in Illinois. Lawrence (19 10) cites instances 



i6o Bulletin 395 

in which the percentage of infected blackberries at certain pickings was 
as high as fifty. 

Even more striking is the fact that in certain localities in New York 
State the growers have been obliged to discontinue the raising of berries. 
They attribute the cause of the failure of the crop to the anthracnose 
disease. In a report of a surv^ey of small fruits in western New York, 
Buchholz (191 1 ) states that by a conservative estimate seventy-five per 
cent of the black raspberry patches were diseased with anthracnose. 
He states also that the average >aeld of the raspberry, at one time, was 
two thousand quarts per acre in this section, while now even in favor- 
able years it is difficult to obtain this quantity. Furthermore a planta- 
tion .formerly yielded a crop annually for a period of from six to seven 
seasons, while in recent years only about four crops are harvested from 
a plantation. That a correlation exists between the general prevalence of 
the anthracnose disease and the reduction in yield of the crop in late 
years is evident. 

SYMPTOMS 

The anthracnose disease appears on the canes, the petioles, the pedicels, 
and the leaves of the raspberry. Lawrence (1910) reports that in Wash- 
ington it occurs commonly on the fruit of the blackberry and rarely on 
the fruit of the loganberry. The writer has not observed these fruits 
to be affected in New York State. 

ON THE CANES 

The presence of the disease is first noticed in the spring when the young 
shoots are about six inches high. Small reddish purple spots, which are 
slightly raised, are seen singly or in groups on the tender canes, first 
appearing a short distance from the growing tip. The spots enlarge slowly, 
and the centers become sunken and assume a pale buff color while the 
advancing margin is raised and purple. A single lesion is more or less 
oval in outline, the greater diameter lying along the shoot; but usually 
the spots anastomose and form irregular blotches which frequently 
encircle the cane (fig. 12, and fig. 13, a). In the center of each spot is 
a small pustule visible to the naked eye. Later in the season, with the 
further growth of the host, longitudinal cracks appear in the spots. During 
the winter these enlarge so that in the spring the second year's growth 
is often split to the pith (fig. 13, b). 

A somewhat different type of lesion has been found on the shoots of 
the purple-cane and red varieties of the raspberry. It differs from the 
spot described above in that a knotty growth develops, which occasionally 
becomes twice the diameter of the normal cane. These knots arise from 
lesions formed when the tissue is very young and tender, and in some cases 
cause a distortion of the cane. This type of injury, which has never 



i 



The Anthracnose Disease of the Raspberry 



i6i 




Fig. 12. ANTHRACNOSE LESIONS OX THE CANES OF RED RASPBERRY 
A severe infection, showing various stages in the development of the lesions 



l62 



Bulletin 395 




Fig. 13. ANTHRACNOSE ON SPECIES OF RUBUS 

A, Lesions on the canes of blackberry; B, lesions on the canes of black raspberry, showing the 

typical fissures 



The Anthracnose Disease of the Raspberry 



163 



been observed on the black raspbem-, was first noticed by Stewart, Rolfs, 
and Hall (1900). 

As a rule the lateral branches are less severely affected than the principal 
canes. Occasionally young laterals are killed when they first develop. 
These branches become dry and the tissue is hard and brittle, while scab- 
like lesions entirely girdle the base and extend up the young shoot. The 
lateral shoots that arise from two-years-old canes and bear the fruit, 
however, are never seriously diseased. Although spots often occur on 
them the lesions are small and cause comparatively little injur>^ 

ON petioles and pedicels 

Anthracnose is not found commonly on the petioles and the pedicels 
of^the raspberry. When it does occur there the spots are similar to those 
on the canes, although frequently the purple margins are absent and the 
affected area is pale buff, raised and scablike. The diseased petioles 
and pedicels become brittle, while the fmit is retarded in its maturation 
in proportion to the severity of the infection. 

ON the leaves 

The disease appears on the leaves of the raspberry somewhat later in 
the season than on the canes. Small purple spots with hght-colored centers 
may appear scattered irregularly over the upper surface of the leaf, or 
they may be found in rows where the leaf is creased or folded (fig. 14). 




Fig. 14. ANTHRACNOSE DISEASE ON THE LEAVES OF RASPBERRY 

The spots occur in rows, but not necessarily on the veins 



i64 



Bulletin 395 



Frequently in the latter case the spots anastomose. Since the lesions 
are very small, about one to two millimeters in diameter, the foliage 
is not injured to any extent by the anthracnose, although later in the season 
the affected leaves may become more or less ragged. It has been observed 
also that in some cases the spots drop out and give the shothole effect 
characteristic of many leaf spots. 

The common leaf spot of the raspberry, which may be confused with 
anthracnose, is caused by a species of Septoria. The lesion differs from 
that of the anthracnose disease in being irregular in outline and pale 
brown in color, with minute pycnidia just visible to the eye. In the 
case of the Septoria disease a yellowing and dying of the leaves occurs. 

ETIOLOGY 

The anthracnose disease of the raspberry is caused by the fungous 
pathogene Plectodiscella veneta Burkholder. 



MORPHOLOGY 



The mycelium of Plectodiscella veneta when mature is hyaline and com- 
posed of minute cells many of which are globose. In all stages the fungus 




Fig. 15. AscocARP of plectodiscella veneta 

Longitudinal section through the ascocarp, showing various stages in the development of 
the ascospores. Outlined with camera lucida from prepared slide. The tissue is somewhat 
shrunken. X 850 

is very local and forms a stroma in the epidermal and subepidermal cells 
of the host. This stroma is frequently subcuticular, but never has it been 



The Anthracnose Disease of the Raspberry 165 

observed to be entirely subepidermal. The tissue of which it is composed 
is in its mature condition hyaline, and varies from a pseudoparenchyma 




Fig. 16. ACERvuLus of plectodiscella veneta 

Section showing the differentiation in the upper and the lower layer of the stroma, also 
the conidiophores arising in groups. Outlined with camera lucida from prepared slide. 
The tissue is somewhat shrunken. X 850 

in the outer area to a plectenchyma next to the host cells. In the leaves 
the stromatic tissue consists only of one to several layers of fungous 
cells. The imperfect stage arises from this stroma both on the leaves 
and on the canes, while the ascigerous stage has been observed to arise 
only from the stroma on the canes. 

The ascocarps of P. veneta are pulvinate, from deep brown to black, 
and about 75 /x in diameter (fig. 15). They are borne singly or in groups, 
and they frequently anastomose and give rise to variously shaped bodies. 
The dark color is due to a layer of thick- walled, brown cells which cover 
each fruiting body. These cells at maturity split apart and expose the 
tissue within, which is hyaline, pseudoparenchymatous, and usually in 
a state of disintegration. The cells of the ascocarps are somewhat larger 
and thinner- walled than those of the stroma. Globose, thick- walled asci, 
from 24 to 30 ,u in diameter, are scattered irregularly throughout the 
interior of the fruit body and either lie against one another or are separated 
by the fungous tissue. The ascospores are borne parallel to one another 
in the ascus. They measure from 18 to 21 ^t in length and from 6.5 
to 8 /x in width, and are hyaline, four-celled, ovate, and slightly curved, 
with constrictions at the septa. The basal cell is larger and more obtuse 
than the apical cell. 

The imperfect stage of P. veneta has been known in literature as Gloeo- 
sporium venetum Speg. vShort, unbranched conidiophores are produced, 
frequently in groups over the surface of the stroma ^ and these bear unicellu- 
lar conidia which are held together in a mucilaginous substance (fig. 16). 



i66 Bulletin 395 

The conidia are hyaline, and from oblong to elliptical and in some cases 
slightly dumbbell-shaped. They are characterized by having an oil globule 
at each end, and they measure from 5 to 7 m in length by from 2.5 to 3 ju 
in width. 

NOMENCLATURE 

The conidial stage of the fungus was first collected by Spegazzini in 
1877 in Italy on Rubus chamaemorus. and was named by him Gloeosporium 
venetttm. In America the organism w^as first mentioned by Burrill (1882). 
He evidently either had not seen Spegazzini's description or considered the 
two fungi to be distinct, since he gives no name to the pathogene. Burrill 
states, moreover, that possibly the raspberry fungus belongs to the genus 
Gloeosporium, but he thinks the fact that the spores are not borne beneath 
the epidermis throws some doubt on its position. ElHs (Ellis and Everhart, 
1887) described the fungus under the name Gloeosporium necator E. & E., 
although previously in a letter to Burrill he had referred it to the genus 
Ascochyta. The similarity of G. necator E. & E. to G. venetum Speg. 
was recognized by Ellis, but the two species were separated by him because 
the latter is foliicolous. From this it is evident that he had not observed 
the pathogene on the leaves of the raspberry. In the following year 
Scribner (1888) pointed out the fact that since G. necator E. & E. agrees in 
all characters with the fungus previously described by Spegazzini, and since 
it occurs on both the leaves and the canes, it should be known as 
Gloeosporium venetum Speg. 

In 1914 the writer (191 4) reported the discovery of an ascomycete 
which he regarded as the perfect stage of this fungus, and in a later paper 
(1917) he showed the connection between the two forms. The fungus 
was given the name Plectodiscella veneta. The only representative of the 
genus Plectodiscella known previous to 191 7 was P. Piri, described by 
Woronichin (1914) as occurring on the leaves of apple and of pear. The 
morphology of the two species is strikingly similar and it is apparent that 
the ascigerous stage of Gloeosporium venetum belongs in the same genus. 
With the exception of the work of Von Hohnel (1909), but little careful 
investigation has been conducted on this group of ascomycetes, and the 
systematic position of the genus Plectodiscella is somewhat doubtful. 
Woronichin merely places it somewhere between the genus Elsinoe Rac. 
and the true discomycetes. When it is considered that the position of 
Elsinoe is also indefinite, the taxonomic position of the genus Plectodiscella 
becomes more difficult to determine. " Both genera, however, show close 
relationship with the order Plectascales, and no doubt should be placed 
there. 



The Anthracnose Disease of the Raspberry 167 

life history 
The ascigerous stage 

During the season of 191 4 the fungus was kept under close observation 
in order to determine when the ascocarps begin their development. 
Repeated examinations of anthracnose lesions on young canes of the 
purple-cane raspberry, at Brant, New York, showed that the ascocarps 
begin to develop dtiring the latter part of the summer. The sexual fruiting 
bodies were found more commonly on this hybrid. The perfect stage 
of the fungus has been collected by the writer also on the black raspberry 
and the red raspberry, while Rees (191 5) has reported it on the blackberry. 

About the middle of August, when the immature ascocarps are first 
observed, they appear as minute spots, from deep brown to black, scattered 
singly or in groups over the buff -colored and sunken part of the anthrac- 
nose lesion. These spots are barely visible to the eye, and only visible 
at all because of the contrast in color with the surrounding tissue. At the 
end of the winter the entire lesion assimies a dark brown hue, and it is 
with great difficulty that the fruiting bodies are then observed, even with 
a hand lens. 

In the early stages of its development the ascocarp is merely a raised 
part of the stroma, the tissue of which is but sHghtly differentiated, and 
the asci have not started to develop. A layer of brown cells covers 
the fruiting body, forming a more or less circular structure which gives 
the appearance of a shield, less perfect, however, than those found in the 
family A/Iicrotheriaceae. The cells near the center of the shield are thinner- 
walled, and with the further growth of the tissue within they soon split 
apart in a stellate manner. By autumn the asci have appeared and are 
found as globose bodies filled with a homogeneous mass of protoplasm. 
In some instances the spores are formed by this time. The fungus may 
pass the winter in this condition. 

In the autumn, or more often the following spring, the asci mature and 
the homogeneous mass of protoplasm gives place to eight four-celled 
ascospores. In the formation of these spores the middle septum is laid 
down much earUer than the other two, and so it is not uncommon to find 
two-celled spores. Later these two cells divide and the mature ascospore 
becomes four-celled. The constrictions formed at the septa during this 
second division are frequently not so great as at the first, or middle, septum. 
Occasionally one of the cells fails to divide and an ascospore of three cells 
is formed. 

During the formation of the spores the disintegration of the fungous tissue 
about the asci takes place, and with the rupturing of the outer layer of the 
ascocarp the asci are exposed. Frequently the asci lying in this exposed 



i68 



Bulletin 395 



condition, surrounded by the remainder of the ascocarp, give the appear- 
ance of one of the true discomycetes. This, however, is brought about by 
the persistency of the outer cells of the shield-like layer which covers the 
immature ascocarp. In the presence of sufficient moisture the exposed 
asci elongate to approximately three times their usual length. This 
process is very rapid and may be observed under a microscope when a 
fragment of tissue containing asci is placed in a drop of water. The lower 
part of the ascus remains fastened in the cavity in which it was borne, 
giving a conical shape to the body which raises itself above the surrounding 
tissue. The spores gather at the tip of the ascus and from there are ejected 
into the air. They have been caught at a distance of one centimeter above 

the lesions. 

Even in a single asco- 
carp all the asci are never 
of the same age, and the 
ascocarps on the same 
cane seem to vary in this 
respect. In 1915 mature 
ascospores were first ob- 
sen^ed about the first of 
June, while other asco- 
spores were not mature 
until later in the summer. 
The ascospores, like the 
conidia, have walls which 
are very gelatinous and 
sticky, and great difficulty 
was experienced in tr^nng 
to pick up single spores by 
means of a glass tube, as 
described by Barber.^ The spores adhere especially to the glass slides, 
and it was impossible to get them into the bore of the tube. Single asci, 
however, could be separated in this manner. 

When placed in tap, rain, or distilled water, or on nutrient agar, the 
mature ascospores ■ germinate very readily. They swell somewhat, and 
within less than two hours a short sterigma is produced from one or each 
of the cells. A sprout conidium is formed, which is from oblong to ellip- 
tical in shape and is identical with the conidia of the fungus borne in the 
acervuli (fig. 17). When fully mature the sprout conidia drop from the 
sterigmata but they do not germinate immediately. After a short period 
of rest, from twelve to twenty-four hours, a germ tube is developed and 

« Barber, Marshall A. On heredity in certain microorganisms. Kansas Univ. sci. bul. 4:3-48. 1907. 




Fig. 17. ASCOSPORES of plectodiscella veneta 

Showing various stages in the formation of the sprout conidia. 
X 1132 



The Anthracnose Disease of the Raspberry 169 

mycelium is formed. When an ascus is placed in a drop of water or on 
agar, the spores within germinate by sending the sterigmata through the 
wall of the ascus and producing the sprout conidia on the outside. These 
in turn germinate. After the production of the secondary spores the 
ascospores shrivel and disintegrate. 

During the spring and early summer the ascospores are ejected from 
the asci. Falling on the young shoots, apparently the spores produce the 
sprout conidia which later send forth germ tubes that penetrate the host 
tissue. Because of their gelatinous walls, the ascospores could readily 
adhere to the smooth surface of the cane and germinate when sufficient 
moisture is present. These steps, however, have never been followed by 
the writer. 

The imperfect stage 

As stated above, Plectodiscella veneta may pass the winter in the asciger- 
ous stage. The ascocarps, however, are very rare and the pathogene as 
a rule winters over as mycelium in the canes. With the usual periods of 
rainfall in the spring, accompanied by warm . weather, a great many 
conidia are produced in the old lesions, and these conidia readily infect 
the young raspberry shoots which at this time are about eight to twelve 
inches high. 

The germination of a conidium on a young raspberry cane has been 
observed only on canes in a moist chamber. Here the spore germinates 
by producing one or more germ tubes, which branch profusely and form 
a minute cushion of cells. The cushion adheres closely to the host and 
is not readily removed, evidently because of the hyphae which have begun 
to penetrate the cell or cells of the host beneath. It is difficult to deter- 
mine whether the minute fungous mass is subcuticular or not. On the 
young shoots of the raspberry used {Rubus neglectus) the cuticle is poorly 
developed. Later, however, when the fungus has spread through the 
epidermal cells, the cuticle may be found to extend a short distance over 
the lesion. After the pathogene has entered the cells of the host, further 
growth continues in the formation of a stroma, the center of which appears 
as a small pustule visible to the eye. This raised part of the stroma has 
nothing whatever to do with the fructification of the fungus, as one is at 
first led to believe, but is merely the accumulation of fungous cells at the 
point of infection. While the tissue of the cane is tender the mycelium 
grows rapidly, but growth is soon checked upon the hardening of the host 
cells at maturity. Consequently a lesion resulting from a single infection 
seldom reaches a width of more than one centimeter. With the further 
tangential growth of the cane underneath the lesion, the stroma is often 
torn apart, and during the second year it is found primarily about the 
edges of the spot. 



170 Bulletin 395 

Shortly after the stroma begins to develop, conidiophores arise, usually 
in groups over the surface, and these bear conidia. The conidia are 
embedded in a gelatinous substance which is soluble in water, and there- 
fore they may be splashed by rain to the surrounding canes. According 
to Appel (191 5), this gelatinous substance which covers the spores also 
aids them in sticking to the heavy wax cuticle of the raspberry cane. 

The conidia germinate within a period of from three to twelve hours in 
water and on various nutrient media, but the writer has never observed 
more than a forty-per-cent germination. From the few observations made 
their vitality appears to be short, although Scribner (1888) was able to 
germinate spores that had been kept in the herbarium for several 
months. Drying the conidia on a glass slide for twenty-four hours does 
not injure their vitality, but repeated drying causes their death. 

It is possible that the fungus dies after the production of conidia in the 
spring, since the writer has found but few conidia in old lesions after early 
summer and these were evidently left from the early production. Further- 
more, spores were never produced when diseased canes that had borne 
fruit were placed in moist chambers, and the writer has never been able to 
obtain cultures of the fungus from plantings of such tissue. The death of 
the pathogene cannot be attributed to the dying of the host after fruiting 
time, as the fungus on one-year-old canes which have winterkilled may 
produce conidia in great abundance the following spring. Here it should 
be remembered that, although raspberry roots are perennial, the canes are 
biennial. The fungus living on the latter has a similar life period, even 
though it is not entirely parasitic on its host. 

PATHOLOGICAL HISTOLOGY 

Very little has been done by previous investigators on the pathological 
histology of raspberry affected with anthracnose. Scribner (1888) states 
that " the greatest injury is confined to the cambium layer, or the portion 
through which the sap is conveyed in the process of growth." Paddock 
(1897) states that " it is not known that the fungus works into the wood 
but its attacks occasionally cause the canes to crack and expose the pith." 
As to the exact tissues invaded by the fungus and the various pathological 
conditions which arise in them, nothing has been written. 

The following observations were made on diseased canes of the Colum- 
bian variety of raspberry. This is a purple-cane variety and possibly is 
more severely attacked by the fungus than are any of the blackcap varieties. 
The lesions frequently develop to a greater extent on the former than on 
the latter, and thus a wider range of stages may be observed. 

Infection takes place more readily on young and tender canes, and 
throughout the summer the small reddish purple spots indicating recent 



The Anthracnose Disease of the Raspberry 171 

infection are found only on the tips of the shoots. During the early 
developnient of the disease the epidermal and the outer cortical cells col- 
lapse. At this early stage the fungus has never been noticed in these cells, 
but since the hyphae are very slender and the dead host tissue becomes so 
deeply stained the m^^celium would be difficult to detect. The paren- 
chyma below this collapsed region is evidently affected with a toxin or 
enzyme either produced by the fungus or resulting from the death of the 
host tissue. The cells in this region divide very rapidly in a tangential 
plane. This hyperplasia of the parenchyma cells causes the young lesion 
to be slightly raised at first on the surface of the cane, but with further 
development of the pathogene this tissue collapses and the lesion becomes 
sunken. A thin stroma then fills the cavity and a very small trace of the 
cortex remains or frequently its destruction is complete. During this 
time the organism continues its invasion of the parenchymatous cells 
between the vascular bundles. A hyperplasia of the phloem next occurs, 
but np further pathological condition arises within this tissue in case of 
late infection. On the other hand, with early and severe infection the 
phloem cells collapse and the fungus destroys the cambium and extends 
to the xylem. 

Normally a ring of fibers is formed in the cortex, which are not in a 
continuous sheet but appear in groups associated with the phloem. If 
the pathogene reaches these before they mature, the fibers become abnor- 
mal or are completely suppressed. After their development, however, 
they are very resistant to the attacks of the fungus. 

The xylem tissue is the least affected by the anthracnose disease, but 
if infection takes place when the vascular bundles are small the xylem 
ceases its normal development. It is difficult to determine whether this 
tissue is. invaded by the pathogene, since only the outer edge shows the 
necrotic condition which might be indicative of the presence of the fungus. 
Frequently it is impossible to determine the position of the cambium, 
as the diseased phloem and xylem lose their distinctive characteristics and 
become fused. Although hypoplasia is exhibited in the xylem beneath 
the infection, it is oft'set by an excessive development of that tissue on 
either side of the diseased spot. This is likewise true of the phloem. 

Because of the increased development of the vascular bundles on either 
side of the lesion, and the hypoplasia and destruction of the tissue within 
the lesion, an uneven growth of the cane results. Longitudinal fissures 
appear in the diseased area and later extend into the xylem and in some 
cases into the pith. This splitting of the cane is caused by the strain 
placed on the diseased tissue due to the continued tangential and radial 
growth of the surrounding normal tissues. It is delayed, however, to 
some extent by the development of a group of parenchyma cells which 



172 



Bulletin 395 



take the place of the phloem and the inner cortex. In cross section this 
group of cells is wedge-shaped, with the apex extending toward the center 
of the cane, and in the outer edge small bundles of fibers frequently may 
be observed. This tissue collapses soon after development and is torn 
apart when the fissures occur in the lesion. 



CULTURAL CHARACTERS 

Miss Stoneman (1898) states that this fungus "does not adapt itself 
readily to artificial culture, and considerable difficulty was experienced 
before obtaining a pure culture." In making plantings of diseased tissue 
the \yriter found that the fungus develops so slowly that contaminations 

are likely to grow 
over it. The 
growth of the or- 
ganism from such 
plantings cannot 
be detected mi- 
croscopically for 
five or six days, 
and a week more 
is required for 
sufficient develop- 
ment before the 
fungus can be re- 
moved to a test 
tube. Spore dilu- 
tion plates are as 
satisfactory a 
method of isolat- 
ing the pathogene 

as any, and conidia are readily obtainable throughout the summer and 
even late in the autumn. A pure culture of the fungus may be obtained 
also by inverting a sterilized petri dish containing a thin layer of nutrient 
agar over a small piece of raspberry cane bearing ascocarps. When the 
piece of bark is moistened the ascospores are ejected from the asci and 
lodge on the agar surface above. The spores can then be located easily 
with a low-magnifying microscope. By marking the position of the spores 
on the lower side of the petri dish their germination and development can 
be observed. The ascospores first produce sprout conidia, but further 
de\'elopment on the medium is identical with that from the conidia of 
the fungus. 




CONIDIA OF PLECTODISCELLA VENETA 

The conidia and conidiophores were produced in culture. Some of the conidia 
are germinating. X 1132 



The Anthracnose Disease of the Raspberry 



173 



The growth of the fungus in culture is very peculiar. Miss Stoneman 
(1898) states that several isolations were made before she was satisfied 
that she had obtained the desired organism. The conidia germinate on 
various kinds of agar within a period of from three to twelve hours (fig. 
18). From a single conidium one or more germ tubes are developed, 
which at first grow rapidly. Septa are formed, the cells become swollen, 
and soon the conidium is indistinguishable from the cells of the mycelium. 
In tap or rain water, growth ceases at this stage. No appressoria have 
been noticed. On potato or nutrient agar, the primaiy germ tubes branch, 
and their cells, which are globose, form a more or less compact mass. The 
colony is circular in outline and as the mycelium grows older the color 
changes to a pale vinaceous pink. Hyphae radiate in all directions from 
the fungous mass but ^only for 
an exceedingly short distance. 
On media containing a small 
amount of agar a more nutri- 
tive growth occurs, the hyphae 
of which are filamentous, with 
occasional globose cells. 

The aerial growth of this fun- 
gus in culture is comparatively 
slow, and continues as a piling- 
up of cells forming a wrinkled 
mass having the appearance of 
sclerotia (fig. 19). In some cases 
this mass has a shining appear- 
ance, while in others fine aerial 
hyphae are formed over the 
compact growth. The color of the culture varies from light russet- 
vinaceous to maroon, while the edges of the colonies are lighter in color due 
to the younger mycelium. The cells of the hyphae in the young colonies 
are very minute but become somewhat larger as they grow older. The 
diameter of the filamentous hyphae is from 1.5 to 4.5 m- while frecjuently 
a globose cell measures as much as 14 /x (fig. 20). 

When the organism is cultured on potato agar containing glucose, 
the growth is much more rapid and aerial mycelium is formed which 
gives a pale brown or white downy appearance to the sclerotial growth. 
With the addition of glucose there is also a reduction, or at least a retarda- 
tion, in the intensity of color production. On potato agar containing five 
per cent of glucose, the culture is pale brown with the characteristic red 
color developing next to the medium. On commeal agar the fungus has 
a brilliant red appearance, while on sterilized bean pods the growth is 




Fig. 19. CULTURE of plectodiscella ven- 

ETA ON POTATO AGAR CONTAINING I PER 
CENT OF GLUCOSE 



174 



Bulletin 395 



sclerotial and from cinnamon buff to maroon in color. On cellulose 
agar the fungus grows very slowly, there being only a slight digestion 
of the cellulose in the immediate proximity of the fungous mass. 

Conidia are seldom produced in culture, and some difficulty was 
experienced in obtaining spores for use in inoculation experiments. It was 
found that a sudden change in the humidity of the culture brought about 

a production of 
conidia in suffi- 
cient numbers for 
use. It is to be 
noted, however, 
that the produc- 
tion of conidia is 
not continuous. 
The fungus was 
removed from a 
dry atmosphere 
to very moist con- 
ditions. This sud- 
den change caused 
a production of 
conidia almost 
immediately, very 
similar to the man- 
ner in which they 
are produced in 
nature. Small 
conidiophores 
Fig. 20. MYCELIUM OF PLECTODiscELLA VENET.-v arisc ovcr the 

The older cells are globose and usually filled with oil globules and red fungOUS maSS and 
pigment. The mycelium is from a culture on potato agar. X 1132 . 1 • 1 

bear conidia which 
are similar to those occurring on the canes. When Plectodiscella veneta is 
growTi continuously under moist conditions, few or no spores are produced. 




INOCULATION EXPERIMENTS 

Inoculations with spores from the Gloeosporium stage 

The proof of the pathogenicity of the fungus depended on its constant 
association with the anthracnose until 1910, when Lawrence made a few 
inoculation experiments. He used the fruits of the blackberry, and inocu- 
lated them with conidia from the leaves and the canes. He was unable 



The Anthracnose Disease of the Raspberry 175 

to obtain spores of Plectodiscella veneta in culture. Typical lesions were 
formed on the drupelets after an incubation period of from fifteen to 
forty-eight hours. 

During the summer of 19 13 the writer conducted a series of inoculation 
experiments on young raspberry canes of the Columbian variety, which 
were emerging from the ground. Cotton-plugged lamp chimneys were 
placed over these shoots, and when they were about six to eight inches 
high they were sprayed with a suspension of P. veneta conidia in water. 
The conidia were taken from the lesions on older canes, and in a few 
cases from pure cultures on potato agar, but in no case did more than 
thirty or forty per cent of them germinate. All inoculations were made 
in the evening, to avoid the evaporation of the drops of water containing 
the spores, and the lamp chimneys were allowed to remain over the young 
plants for two or three days. Check plants were used. Many of these 
experiments were destroyed, as they were conducted in a field which was 
being continuously cultivated. The final data obtained, therefore, were 
relatively few and scattered. 

Inoculations were made on the following dates: May 26, June 20 and 
23, July 16, 18, and 29, and September i. Fifty-six of these experiments 
were completed but infection occurred only in eighteen cases. The 
incubation period was three days for seven experiments, four days for 
four, five days for five, and seven days for two. The shortest period 
was during the warmest weather, while during cool weather no infections 
occurred. Aside from climatic conditions, the causes of the low per- 
centage of infection were possibly poor germination of the conidia, the 
drying of the drops of water, and the condition of the host plant. When 
the host tissue becomes hard, infection does not take place. Other factors, 
not sufficiently understood, no doubt entered into the experiments. 

Inoculations with spores from the ascigerous stage 
In order to make certain the connection between the ascigerous form 
and Gloeosporium venetum Speg., a series of inoculation experiments 
were conducted. The use of ascospores as an inoculum was impossible, 
since very few could be collected owing to the scarcity of the ascocarps 
and their irregularity in time of maturing. Also, it is difficult to make 
certain that the ascospores are separated from the conidia unless the 
former are collected by causing them to be ejected on plates of agar. 
The most satisfactory method appeared to be the use of conidia for 
inoculation from a culture of the fungus that had been developed from a 
single ascospore. 

Such a culture was obtained, and was grown on three-per-cent potato 
agar until large, sclerotia-like masses were formed. These fungous 



176 



Bulletin 395 



masses were then transferred to sterilized bean pods in tubes containing 
several centimeters of water. The bean pods served primarily as supports 
on which the fungus could be placed above the water. The cultures were 
then placed in aiiaiyubator at a temperature of 24° C, and by the end 
of three days a sufficient number of conidia were produced. By dropping 
the fungous mass into a small quantity of water the spores readily fell 
off and could be sprayed on the infection court. The germination of these 
conidia was fairly rapid, a germ tube being developed in about live hours; 

but the proportion of germination 
was low, in most cases between 
five and ten per cent. 

Early in the winter of 1914-15 
a number of roots of the Colum- 
bian variety of raspberry were 
planted in the greenhouse. Owing 
to the earliness of the dormant 
jjeriod and to the unfavorable 
conditions within the greenhouse, 
the plants grew slowly and gave 
a ver>' stunted growth. All in- 
oculation experiments with these 
plants gave negative results. As 
already stated, the anthracnose 
lesions appear only on tender 
succulent canes, and apparently 
the canes which had developed 
slowly on the green -house plants 
were too hard and woody for the 
fungus to infect. 

Later, about the first of March, 
191 5, a few raspbeiTy plants of 
a red variety, which were tender 
and growing rapidh-, were pro- 
cured. On March 4 two canes were sprayed with a suspension of conidia 
from a culture of the fungus developed from a single ascospore, and the canes 
were covered with bell glasses lined with moist filter paper. These glasses 
were plugged at the top with cotton and allowed to remain over the canes 
for two days before removing. Two other canes in the same bed remained 
untreated. On March 20, small purple spots had appeared on one of 
the canes. These infections grew slowly, much more slowly than an 
anthracnose lesion developing in the field, but spots typical of those caused 
by Gloeosporium venetum were produced. Microscopical examination of 
the spots showed conidia of Gloeosporium venetum. 




Fl(.. 21. .\NTHkACKOSE LESIONS ON C.-VNKS OK 
Hl.ACK RASPBERRY PRODUCED By ARTIFICIAL, 
INOCULATION 

The canes were inoculated on April 13, 1915, with 
spores from a culture of Plectodisrella veneta which had 
developed from a single ascospore 



The Anthracnose Disease of the Raspberry 177 

Again on April 15 four tender canes of a blackcap variety of raspberry 
were sprayed with a suspension of conidia as above. Bell glasses were 
placed over them as in the previous experiments, and one check plant 
was used. A sample of the conidia used was placed in a drop of water 
on a slide, and about eight per cent of the spores germinated. After 
about a week, on April 21, a number of small purple spots had appeared 
on the four canes and these later developed into typical anthracnose 
lesions (fig. 21). The check plant remained normal. 

Cross-inoculatio ns 

Although no cross-inoculation experiments were conducted to test the 
ability of the pathogene isolated from one species of Rubus to infect 
another species, some data regarding this are at hand. In the experi- 
ments described above, the culture of the fungus from a single ascospore 
was isolated from the hybrid known as Rubus neglectus. The palhogene 
then produced infection on both Rubus occidentalis and Rubus idaeus 
var. actdeatissimus. The cultural characters of the fungus isolated from 
these three species, as well as from the blackberry {Rubus sp.), are 
identical. 

THE EFFECT OF WEATHER CONDITIONS 

Practically nothing is known as to the exact effect the diseased canes 
have on the yield of fruit. No experiments have been conducted to 
determine the relationship and it is very difficult to estimate. Obser- 
vations show, however, that the decrease in yield due to the disease varies 
considerably with weather conditions. This variation may be attributed 
largely to the fact that both the pathogene and the canes are biennial. 
The infection period of the fungus is during the early summer when the 
canes are in their first year's growth, while fruit is not produced until 
the second year. Therefore the weather conditions that prevail both 
throughout the infection period and at fruiting time influence the yield. 
If during the first year's growth of the canes there is an abundance of 
rain and damp cloudy weather, the young shoots in a field where the 
anthracnose exists become severely diseased. Such weather is effective 
only the first part of the season, as practically no infection occurs after 
July. Furthermore, if dry weather prevails the following year when the 
canes produce fruit, the berries mature under very unfavorable conditions. 
They are subject not only to the dry weather, but also to the diseased 
condition of the canes where the conductive tissue is impaired. It is 
during such combinations of seasons that the loss to the raspberry crop 
is so noticeable, while in a season when there is plenty of moisture the 
diseased canes may produce a good yield of berries. 



178 Bulletin 395 

Canes that are afYected with anthracnose are, as a rule, more susceptible 
to winter injury than are unaffected canes. In a field in which the disease 
is present, the canes that are found to have been killed during the winter 
are the ones that were severely affected by anthracnose and other diseases. 

CONTROL 
CULTURAL METHODS 

It has been observed by the writer that cultural methods greatly favor 
the distribution of the pathogene to the new raspberry plantings. The 
method of propagation of the blackcap and the purple-cane raspberry 
is no doubt accountable for this. These varieties are propagated by means 
of tip layers, which many growers do not remove in the spring until the 
young shoots have reached a height of a foot or more. By this practice 
it is maintained that the young plants are afforded a better chance of 
development. However, during this period the old diseased canes act 
as a source of inoculiim to the new shoots, which become infected and thus 
the disease is carried to the new plantation. On the other hand, if care 
is taken to dig the roots before they sprout or before the fungus on the old 
canes sporulates, which in New York State is sometime near the middle 
of May, a healthy setting can be obtained. In the case of the red varieties, 
which it is necessary to propagate by means of suckers, the young plants 
should be procured from fields where it is known that anthracnose does 
not exist, or the canes should be carefully examined for lesions of the 
disease. The red varieties of the raspberry are veiy resistant, and there- 
fore it is not uncommon to find a field free from the disease, from which 
young suckers may be selected. As a raspberry plantation is com- 
paratively short-lived, the selection of healthy plants at the beginning 
is a long step in the control of the disease. Moreover, observations 
indicate that the pathogene does not spread rapidly from one field to 
another. The character of the fungus would further substantiate this 
\'iew, as the sticky walls of the conidia render them not readily adapted 
to dissemination by the wind. 

The eradication of anthracnose after it has once become established 
in a field is a difficult process. Pruning out the diseased canes has been 
recommended, but this is not desirable in the majorit}- of cases since 
usually the disease has become widely spread before it is noticed and 
without the entire eradication of the sources of inoculum but little good 
can be accomplished. Sturgis (1900) cites an instance in which the 
majority of infected canes were removed and the disease was checked. 
The season was dry, however, and this probably accounts for the re- 
duction in infection. No doubt the remcn'al of o"d canes immediately 



The Anthracnose Disease of the Raspberry 179 

after the fruiting season is good cultural practice, but from the stand- 
point of checking the disease it is beneficial only in obtaining better 
aeration. Thorough cultivation, especially the eradication of weeds, like- 
wise is advantageous, or any measure that has a .tendency to keep the 
canes free from persistent moisture. 

SPRAYING 

Niimerous atterhpts have been made to control anthracnose by spraying, 
but the results in most cases have been questionable. Since he found 
the raspberry disease so similar to anthracnose of the grape, Scribner 
(1888) recommended spraying with iron sulfate when the plants were in 
a dormant condition, and using bordeaux mixture if subsequent appli- 
cations were necessary. 

Paddock (1897) conducted spraying experiments in a black raspberry 
plantation for three years with doubtful results. At least he came to 
the conclusion that spraying was not a profitable operation, but the 
data given by him -may be interpreted otherwise. His experiments 
briefly are as follows: 

The first three rows in the raspberry plantation were sprayed when 
domiant with copper sulfate, using three pounds to eleven gallons of water; 
the next three rows were treated with a saturated solution of iron sulfate 
in water; the last three rows were left unsprayed. This plan was repeated 
five times. The two treated series were then followed with five appli- 
cations of bordeaux mixture. The yields of berries are given on the three 
series for three years. The spraying was begun in 1894, and therefore 
the yield in 1895 was the first on treated canes. The yield in that year 
was much increased over that of the preceding year. For the treated 
rows there was an increase of 171 per cent and 148 per cent, respectively, 
while for the check row the increase was only 39 per cent. In 1896 there 
was not such a great difii'erence in the yields, but the infection, even on 
the check rows, was very slight. Paddock compared his data one year 
at a time and did not take into consideration the fact that the spraying 
of the canes one season affected the yield the following year. Therefore, 
with the present inter^Dretation of the results obtained by Paddock, there 
seems to be a pronounced indication that spraying would be profitable, 
at least in years when the anthracnose infection is severe. 

Rees (191 5) claims that blackberry anthracnose in the northwestern 
United States can be controlled by spraying. This, however, is hardly 
comparable with spraying for the cdntrol of the same disease on the 
Taspberrv\ The benefit derived from treating the blackberry plant is in 
preventing berry infection, while on the raspberr}^ the fruit is never 
infected. 



i8o Bulletin 395 

During the summer of 191 1 Dr. P. J. Anderson conducted spraying 
experiments in raspberry fields at Brant, New York. This work was 
continued by J. H. Muncie during the summer of 191 2, and by the writer 
during the seasons of 19 13 and 191 4, after which the experiments were 
brought to a close. A large number of spray materials, alone and in 
combination, were used. The results of the experiments were recorded 
for the most part on the basis of percentages of infected canes. This 
in itself is unsatisfactory, as it does not show the severity of infection 
and gives no indication as to the effect of the spray on the yield of fruit, 
which is really the ultimate aim. Thus very little data were obtained 
indicating that spraying was effective. 

A few well-checked experiments, however, are worthy of recording. 
In two plats, each containing approximately one hundred and thirty-two 
bushes, three applications of bordeaux mixture, 4-4-50, reduced the 
ntmiber of diseased canes to 23 per cent and 16 per cent, respectively, 
while the untreated bushes showed infection to the extent of 77 per cent 
and 71 per cent, respectively. The first applica.tion was made when 
the young shoots were from eight to ten inches high, and the following 
applications were made at intervals of two weeks. These experiments 
were repeated for several seasons, with similar results. After the third 
application the ripening of the fruit prevented further treatments, although 
the lateral branches were not fully mature and occasionally during this 
period infections occurred. These infections were observ^ed only in a few 
cases, however, and then they were not severe. Spraying after fruiting 
time is useless for several reasons. Infections seldom take place late 
in the season, and furthermore the new growth that develops after August 
is removed when the plants are pruned the following spring. 

Besides bordeaux mixture various other chemicals were used. Lime- 
sulfur, self -boiled lime-sulfur, and iron sulfate were tested, but none of 
these gave satisfactory results. The adhesive quality of the iron sulfate 
in combination with the other spray materials also was investigated, but 
sufficient benefits were not obser\^ed to warrant recommending its use. 
Lime-sulfur, i gallon to 40 gallons of water, precipitated with iron sulfate, 
7 1 pounds to 100 gallons, gave a reduction in the percentage of infected 
canes. The spraying, however, dwarfed the plants considerably, cavising 
them to bear small fruit with an insipid flavor. Bordeaux, on the other 
hand, caused only a slight burning of the tender leaves. 

The application of a spray solution when the plants are in a dormant 
condition, as suggested by several investigators, was tested thoroughly 
during four seasons. Various strengths of iron sulfate, the greatest 
being 2 pounds of the material to i gallon of water, copper sulfate 4 pounds 
to 50 gallons of water, and lime-sulfur i to 8, proved to be of no benefit. 



The Anthracnose Disease of the Raspberry 



i«i 



¥ 



The chemicals evidently do not penetrate far enough into the lesions to 
kill the pathogene, or else they fail to remain on the plants for a sufficient 
length of time to prevent the fungus from sporulating. Although the 
iron sulfate did not injure the buds, it caused the canes to turn black, 
giving the plants the appearance of having been burned over by fire; 
but this caused no harmful effects to the plants. This blackening of the 
canes was observed on the Columbian variety, and whether or not it 
occurs on all varieties of the raspberry is not known. 

The yield of berries was recorded in only one experiment. On two 
rows, with approximately sixty-six bushes each and with 44 per cent 
of the canes diseased, there were estimated to be about 360 quarts more 
per acre than on two check rows with 90 per cent of the canes diseased. 
The treated plat had been sprayed with bordeaux and was separated 
from the untreated plat by two rows. This is but an indication that 
spraying is beneficial, and no adequate conclusions can be drawn from 
so small an experiment. More data relating to the effect of diseased canes 
on the yield of the fruit are needed, and until they are obtained no con- 
clusive proofs can be furnished that spraying to combat the anthracnose 
of the raspberry is a profitable practice. 



I 



i82 Bulletin 395 



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BuRKHOLDER, W. H. The perfect stage of the fungus of raspberry 

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7:83-91. 1917. 
BuRRiLL, T. J. Blackberry and raspberry cane rust. In Notes on 

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Craig, John. Anthracnose of the raspberry (Gleosporium venetum). 

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The Anthracnose Disease of the Raspberry 183 

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